The invention relates to a spindle motor for hard disc drives, in particular a spindle motor with sleeve according to the generic term of present invention.
In general spindle motors comprise a stator and a rotor turnably borne about a central shaft with respect to this. The bearing occurs by means of rolling bearings, in which the shaft is either joined in fixed position with the stator, or is turnably borne together with the rotor.
In particular, the invention relates to so-called base-plate or basis-plate motors of the last-mentioned type, consisting of rotor, stator and base plate, in which the shaft firmly joined with the rotor is turnably borne with the aid of rolling bearings with respect to the stator fastened indirectly or directly to the base plate. The outer, fixed parts of the roller bearings, therefore the outer rings, are fastened there ordinarily in a shell or sleeve (Milse) open at both ends, which is either an internal component of the base plate or is installed in this as a separate member. The outward-directed opening of the sleeve is covered off and sealed gas-tight.
A disadvantage of the construction described is that for the covering-off of the sleeve opening an additional part is needed, the hermetic sealing-off of which, preferably by means of a liquid sealing agent (bonding agent) is functionally critical, expensive and timeconsuming.
Further disadvantages lie in that motor-relevant parameters are checkable only after the mounting of the rotor in the base plate on the fully assembled motor, so that possible faults cannot be detected until this stage, in which the mounting of the rotor in the base plate is rendered difficult by magnetic forces and moments.
The problem of the invention lies in improving a spindle motor with sleeve for solid-plate running gears, i.e., hard disc drives, in such manner that, on the one hand, the sealing problems addressed above are eliminated and, on the other hand, a more advantageous assembling and testability of the motor are given.
This problem is solved by the features of present invention.
The invention is distinguished by the separate pot-shaped sleeve closed on one side, on the outer circumference of which the stator is held, and on the inner circumference of which the outer rings of the rolling bearings are held. The sleeve serves, therefore, as assembling aid for the rolling bearings and for the stator.
By reason of the feature that on the outer circumference of the pot-shaped sleeve the stator is held, and on the inner circumference the rolling bearings are held, the motor can already be completed in the base plate and tested before the end of its construction.
There, with the mounting of the thus prefabricated unit into the base plate, no hampering magnetic forces arise.
Further, there is the additional advantage that the member required for the covering-off of the sleeve opening is eliminated, and the sealing-off of the fit between sleeve and base plate can be done very much more simply.
Advantageous further developments and modifications of the invention are yielded from the dependent claims.
It is provided, accordingly, that the sleeve consists of a plastic material. This offers the advantage that a noise damping takes place. Since the sleeve according to the invention surrounds the ball bearings radially externally, the noises that proceed from the bearings are damped.
It is just as possible, of course, to make the sleeve of metal or of a metal alloy.
As an assembling aid for the stator, the sleeve can have a step or a collar on its upper open end, on which the stator bears.
For the reception of the motor, on the base plate there is provided a corresponding interruption into which the sleeve is installed true to measure, and fastened by a preferably sealing cementing. After installation of the motor into the base plate, the interruption is closed from the bottom of the sleeve. A sealing of the fitting joint between sleeve and base plate prevents the penetration of contaminated air from the environment into the interior of the hard disc drives. Simultaneously the bearing system is bounded by the base integrated into the sleeve, so that no dirt particles can force their way from the outside into the bearing system.
The inventive object of the present invention is yielded not only from the object of the individual patent claims, but also from the combination of the individual patent claims among one another. All of the data and features disclosed in the documents, inclusive of the abstract, especially the spatial construction shown in the drawing, are claimed as essential to the invention insofar as, individually or in combination, they are novel with respect to the state of the art.